Assimilation Efficiency of Sanderlings (Calidris alba) Feeding on Horseshoe Crab (Limulus polyphemus) Eggs

The Role of Horseshoe Crabs in the Biomedical Industry and Recent Trends Impacting Species Sustainability

“…An estimated 107 billion horseshoe crab eggs are necessary to support 423,000 shorebirds flying into Delaware Bay to feed before continuing on to their breeding grounds (U.S. Fish and Wildlife Service Shorebird Technical Committee, 2003). For example, when preparing for migration, sanderlings consume an average of 8,300 horseshoe crab eggs per day; ruddy turnstones, a daily average of 13,300 (with a peak daily consumption of 19,360 eggs); and red knots consume an average of 18,350 (with a peak consumption of 23,940 eggs/day) (Castro et al, 1989;Haramis et al, 2007).…”

The Horseshoe Crab, Limulus polyphemus: 200 Million Years of Existence, 100 Years of Study

“…As food is often scarce along their migration route, Delaware Bay, with its vast supply of horseshoe crab eggs, is a crucial stopover for the shorebirds to obtain food and rest (Clark et al, 1993). Castro et al (1989) report that during the 2 to 3 week time period the birds stay on Delaware Bay, they undergo weight gains of at least 40% of their body weight. It has been estimated that all shorebirds consume 5526.2 × 10 6 kJ of energy for their trip, equivalent to approximately 539 metric tons of horseshoe crab eggs (Castro and Myers, 1993).…”

“…It has been estimated that all shorebirds consume 5526.2 × 10 6 kJ of energy for their trip, equivalent to approximately 539 metric tons of horseshoe crab eggs (Castro and Myers, 1993). One reason this number is so large is because of the low metabolic efficiencies of the birds, which Castro et al (1989) attribute to the low number of eggs that are actually broken down when passing through the birds' gastrointestinal tracts, as the egg's cuticle resists chemical and enzymatic digestion.…”

“…The sanderling (C. alba) averages a metabolic efficiency of 38.6% +/-1.0% (Castro et al, 1989). The value of assimilation efficiency is assumed to be similar for all species, because assimilation efficiency seems to be primarily a function of food consumed (Castro et al, 1989;Castro and Myers, 1993).…”

“…The value of assimilation efficiency is assumed to be similar for all species, because assimilation efficiency seems to be primarily a function of food consumed (Castro et al, 1989;Castro and Myers, 1993). Thus, it has been estimated that 1,820,000 female horseshoe crabs are required to feed Delaware Bay's migratory birds (Castro and Myers, 1993).…”